So I downloaded the iPhone app: Decibels by David Bannach. I created this thread so that it serves as a guide for how loud aftermarket exhausts are. Since videos never do justice of how an exhaust sounds so I thought at least we can see how much louder they are than stock in further aiding the decision buying process. As a rule of thumb lets keep this app and keep the phone about a foot away from the exhaust. My results:

Stock Exhaust:

Cold start:90db

Idle:73-75db

If anyone wants more revs or other readings let me know for the stock exhaust. I know this app may not be the most accurate but if we all use the same one and all get the readings from about a foot away from the exhaust we will have a good basis of how different exhausts are read. Everyone post!

Could you post up a photo of exactly how and where you hold the phone to give us a benchmark to work to.

eg, do you hold the iphone on the sides with the front face facing the exhausts directly, and a foot back at the same height?

I knew I should have included this in the oringal post. I held the phone first off facing the exhaust tips so the screen of the iPhone is facing the exhaust. At about a foot away I would say I pretty much kept the iPhone straight up and held the phone about half a foot off the ground. So you can see the phone is directly in front of the exhaust while keeping a good distance. Obviously I had to squat down and hold the phone.

Im in for readings. This is a GREAT idea. Standardizing it would be good though so one can do a brief overview and get information needed. This really would help a lot of folks. Wheres the kudos button for rjd598???
i.e:
Exhaust: XX Brand
Outside:
-Cold Crank
-Idle
-Cruise (or anything else deemed appropriate)
Inside:
-Cold Crank
-Idle
-Cruise (or anything else deemed appropriate)

Im in for readings. This is a GREAT idea. Standardizing it would be good though so one can do a brief overview and get information needed. This really would help a lot of folks. Wheres the kudos button for rjd598???
i.e:
Exhaust: XX Brand
Outside:
-Cold Crank
-Idle
-Cruise (or anything else deemed appropriate)
Inside:
-Cold Crank
-Idle
-Cruise (or anything else deemed appropriate)

thanks man! some other thread was talking about this and i thought to myself why not find a free app and then everyone can join in and we all can benefit. i think as time goes more and more people will chime in and add in what they have. there are definitely more tests that can be done like you said that would even further help the community

Here is a basic guidline for decibel testing for most state an other testing agencies. We use the same process when we decibel test our exhausts.

Put on ear protection. Stop the vehicle on a solid flat surface and leave it running. Prepare a noise testing spot that is at least 25 feet away from any building or enclosed fence wall to avoid echo.

Place the microphone of a decibel meter even with the level of the center of the muffler exhaust opening. Locate the microphone 19 1/2 inches behind the tail pipe at a 45-degree angle to the opening. The microphone cannot be in the direct gas path from the exhaust.

Set the decibel meter weighting for human ear frequencies, not the low frequency setting used to measure music. Several meters use "A" for ear frequencies and "C" for lower frequencies. Set the decibel range for the legal limit. That sets the maximum sound allocation in the center of the needle sweep on the meter. Most localities set an absolute maximum between 90 and 100 decibels. Set the timing for either fast or slow for metering exhaust sound.